Gas detection is a critical capability in many industries that handle or produce chemicals and various gaseous materials. In particular, greater demands in the technology of gas leak detection have arisen for a number of reasons, including industrial efficiency, health and safety considerations, and environmental regulations. Gas detectors are widely used in many environments—industrial plants, refineries, waste-water treatment facilities, vehicles, and homes, to name just a few. Carbon dioxide, carbon monoxide, methane, butane, and hydrogen sulfide are some of the gasses that often require detection and/or monitoring.
Many prior art systems and techniques are available for different types of gas detection. Examples include photo-ionization; flame ionization; photoacoustic techniques; infra-red (IR) absorption; open-path gas cell IR-sensing; electrochemical sensing; gas chromatography; and a wide range of spectroscopic techniques. Some examples of the spectroscopic class are laser absorption spectroscopy, wavelength modulation absorption spectroscopy; cavity ring-down spectroscopy (CRDS), and fourier transform infrared spectroscopy; as well as spectroscopic versions of the above-mentioned photoacoustic techniques.
Many of the techniques mentioned above are useful in various situations that involve gas detection. However, most of them also present some disadvantages in practice. For example, the open path gas cell IR sensors are widely used for gas monitoring. While useful in some situations, gas detection is localized in these systems, and a distributed sensing network would require multiple gas cells. Also, the optical components in the gas cells require very accurate alignment, and this can result in high system cost. Moreover, standard laser absorption spectroscopy techniques such as TDLAS can advantageously detect very low concentrations of selected gasses, but they also require complicated drive electronics and expensive system components. Additionally, integration of TDLAS into a distributed sensing network can be complicated, and can lead to a bulky system.
Potentiometric and amperometric sensing techniques are usually solid state-based, and involve the use of an electrolytic liquid or gel in which two identical electrodes are incorporated. A gas sample being analyzed passes through an associated membrane, and oxidizes or becomes reduced at one of the electrodes, based on the composition of the sample. The electrical potential or current is measured across the electrodes, to determine the quantity of the gas.
While these types of techniques may be specifically effective for accurately analyzing multi-gas mixtures, they also appear to have some drawbacks. For example, the types of gasses that can be analyzed with these techniques may be limited. Also, the techniques may not be able to discriminate between different types of organic compounds. Moreover, membranes that are a necessary component are prone to damage; and frequent calibration of such a system may be required. Furthermore, the potentiometric/amperometric nature of these techniques requires a number of electrical connections, and may also require remote monitoring. This would probably necessitate the use of power-consuming wireless systems, adding to the overall cost of the system.
With these concerns in mind, new gas detection systems would be welcome in the art. The new systems should be able to both detect a gas species of interest, and to accurately determine its location, e.g., with good sensitivity. The systems should also be relatively simple in design, and faster than systems such as gas chromatography. These advanced detection systems should also allow for easy placement near a gas source, e.g., without requiring critical optical alignment, which is often required for cavity techniques like CRDS. The new detection systems should also be relatively economical, in terms of both set-up and operation.